Add video codec setting to AppRTCMobile on iOS.

List items in settings menu no longer stay selected. Checkmarks are now
added to the selected options before the view appears.

BUG=webrtc:7316
TBR=denicija

Review-Url: https://codereview.webrtc.org/2735303004
Cr-Commit-Position: refs/heads/master@{#17296}
diff --git a/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h b/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
index 60ef700..0feb015 100644
--- a/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
+++ b/webrtc/examples/objc/AppRTCMobile/ARDAppClient.h
@@ -60,7 +60,8 @@
 @property(nonatomic, weak) id<ARDAppClientDelegate> delegate;
 // Convenience constructor since all expected use cases will need a delegate
 // in order to receive remote tracks.
-- (instancetype)initWithDelegate:(id<ARDAppClientDelegate>)delegate;
+- (instancetype)initWithDelegate:(id<ARDAppClientDelegate>)delegate
+                preferVideoCodec:(NSString*)codec;
 
 // Sets camera constraints.
 - (void)setCameraConstraints:(RTCMediaConstraints *)mediaConstraints;